Magnetic compass



June 21, 1960 c. L. FRISBIE MAGNETIC COMPASS 3 Sheets-Sheet 1 Filed Feb. 4, 1955 INVENTOR 2 5; dlareL/Hsbie ATTORNEYS June 21, 1960 FRlsBlE 2,941,307

MAGNETIC COMPASS Filed Feb. 4%5 3 Sheets-Sheet 2 INVENTOR Clare Lihlsbi ATTORNEYS June 21, 1960 c. 1.. FRISBIE 2,941,307 MAGNETIC COMPASS Filed Feb. 4, 1955 3 Sheets-Sheet :s

INVENT OR ATTORNEYS United States Fatent Gfiice Patented June 21, 1960 MAGNETIC COMPASS Clare L. Frisbie, 603 De Witt St., Syracuse, N.Y. Filed Feb. 4, 1955, Ser. No. 486,060

Claims. (Cl. 33-223) This invention relates to a direction indicating device, inclinometer, gradient meter and accelerometer but more particularly to a compass that finds unique utility when used with a vehicle including an automobile, a boat, an aircraft, a train etc.

Prior to the advent of the present invention, many devices were available which functioned as direction indicating means. In many cases, such devices have been of the type that included a magnetic element in the form of a ball supported in gimbals to leave the ball freely rotatable about at least two axes. In some instances, the ball has been mounted in a damping fluid with the aid of a plurality of prongs or similar elements which serve to maintain the position of the ball in the fluid without interfering with movement of the ball.

It is a principal object of the present invention to pro vide a novel direction indicating device including a ball element containing one or more magnetic elements, preferably in the form of bars, mounted in a suitable fluid through the agency of a pair of bearings which accurately position the ball in the fluid while at the same time permitting universal movement of the ball;

It is a further object of the present invention to provide a direction indicating device of the type above re ferred to composed, in all parts except the magnets, of any suitable non-permeable material such as plastic'or non-ferrous. metal and characterized by a simple economical structure.

It is a still further object of the present invention to provide a magnetic compass for a vehicle such as an automobile which will, in addition to functioning as a direction indicating means, also function as an accelerometer and inclinometer.

Other and further objects of the present invention will become readily apparent from a detailed consideration of the following description when taken in conjunction with the appended drawings in which:

Figure 1 is a view in front elevation of the preferred form of the present invention;

Figure 2 is a view in section of the device shown in Figure 1 taken along line 2--2;

Figure 3 is a view in section of the device taken along line 3-3 of Figure 2;

Figure 4 is a view in section of Figure 3;

Figure 5 is a fragmentary sectional view similar to taken along line 4 4' Figure 3 showing in greater detail the weight and bearing support for the ball element;

Figure 6 is a view in section showing an alternative form of the present invention;

Figure 7 is a view in front elevation of the modification shown in Figure 6;

Figure 8 is a view in section taken along line 8- -8 of Figure 6;

Figure 9 is a view in front elevation showing a fur-- ther form of the present invention; and I Figure 10 is a view in section taken along line 10-10 of Figure 9.

Referring now to the drawings in detail, Figures 1 to 5 inclusive show the preferred form of the present invention. The direction indicating device shown in these figures consists generally of an outer casing 20 in the form of an annular hemispherical element, the mouth of which is closed by a cover 21. The casing 20 and cover 21 define an internal fluid-tight space. A plug 22 is arranged in the casing 20 to permit filling of the internal space with a fluid suitable for the purposes of the present invention. The fluid selected, however, must be such that its density is great enough so that the fluid will just float the ball. Actually, the reverse procedure is the more feasible and for this reason is recommended. The ball should be weighted to have a composite density equal to that of the liquid medium so as to be suspended in the liquid mediu Mounted within this internal space is a ballmember 23 arranged with the necessary indicia to perform its function as a direction indicating device. More specifically, the equator of the ball member 23 is marked with a series of spaced lines 24 and the necessary letters 24' to indicate the four points of the compass. The letters 24' are, of course, spaced 90 apart as will be evident from an inspection of the drawings. Further, although not shown, it will be appreciated that the space between the letters 24' can be graduated into degree markings suitably numbered to enable a more accurate determi nation of. heading. The ball member 23 is supported Within the casing 20 by means of a pair of bearings 25, one located at the top of the ball member 23 and the other located at the bottom of the ball member 23. These bearings are in the form of cups and are maintained in their proper position through the use of an annular bearing support ring 26 which is welded, cemented, fused, or otherwise joined to the casing 20 about its outer periphery and to the bearing cups 25 about its inner periphery at the points at which it comes in contact with the bearing cups 25. The cup-shaped mem bers 25 are segments of spheres with the radius of each segment being no more than is necessary to retain the ball member 23 within the cups 25. It is preferred that the cup-shaped members 25'be substantially concentric with the ball member 23.

The ball member 23 houses a pair of bar permanent magnets 27 which are mounted within the ball member 23 in the following manner. The ball member '23 is composed of a lower-casing element 28 which has two pairs of brackets 29 molded onto the interior of the casing element 28 about its mouth. The bar magnets 27 fit into the pairs of brackets 29 and are securely retained therein by any suitable means. The rim of the casing element 28 is cut out to form a shoulder as will be seen from Figure 3 and a cover element 30 fits on the shoulder of the cut out of the casing element 28. The two'parts 28 and 30 are fused, welded, cemented or otherwise joined together in a fluid-tight manner so that the passage of fluid through the joint to the interior of the ball member 23 will be prohibited. In addition, a weight 31 is cemented or otherwise secured to the bottom of casingelement '28. As shown in Figures 3, 4 and 5 theweight 31 defines a central bore in which is received a shaft 45 having its lower end cemented or otherwise fixed to the interior surface of the ball 23 in the area of contact. In assembly the weight 31 is slidable vertically relative to shaft 45 whereby its exact I surface of ball member23 will be a contributing factor tn the response of the device and by this. means, good control can be had in producing devices with the desired response.

Once the weight 31 is properly located, it is'cemented, or otherwise attached to shaft 45 so that its position'will remain unchanged. The shaft 45 provides a; means whereby the production of: devices herein described can be standardized regardless of the intended use for the devices or the variety of responses required for the devices, inasmuch as the response can be set by altering theposition of the weight 31 relative to shaft 45.

To the bottom of the casing 20; is connected a com,- pensator casing 32 as by cementing or welding. This casing 32 serves to house a pair of compensator shafts 33, the axesof which are disposed at right angles. Each compensator shaft 33 contains a pair of bar compensator magnets, 34, the function of which is fully known and appreciated in the art.

The cover 21 is marked with a lubber line 35' against which the indicia, of the ball member 23 align to provide a reading of heading. In addition, the cover 21 is also provided with suitable markings 36 to enable the device to function as an inclinometer. In this respect, it will be noted that the weight 31 will serve to maintain the ball member 23 in an upright position in the absence of acceleration or deceleration forces. Hence, tilting of the overall device relative to a plane normal to the gravitational pull will result in relative rotation between the ball member 23 and the cover 21 about a horizontal axis and thus producing an indication on the face of the cover21 ofinclination. Further, the cover 21 is marked or etched, with parallel lines 42 and 43 between v which the spaced lines24 are visible through cover 21.

In order to mount the devce, a ball screw 37 is provided to cooperate with a suitable clamping means and supporting bracket such as the one shown in Figure 6. It; will be appreciated, however, that many means may be employed to mount the device so long as the mounting is made secure.

The bearing cups; 25 will as aforementioned serve to hold the ball member 23 in position within the casing'20. Also, as aforementioned, the internal space within, the casing 20 is filled with a suitable fluid. The operation of the device is such that a thin layer offluid will be present between the bearingcups 25 and the ball member 23. This thin layer of fluid is indicated by the-numeral 38 in Figure. 5. The ideal case would probably be having the layer of fluid between the ball member'23 and the.- supporting cups 25 of, about monomolecular thickness. This fluid willact as a lubricating medium between the ball member23 and the bearing cups 25 to insure the ball member 23 being freely movable in its, support. In actual practice it has been found that the cups '25 can be spaced slightly from the ball member 23 permitting a small amount of play.

Referring now to Figures 6 to 8 inclusive, a modification of the present invention is shown. In this particular instance it will be noted that the device, as, before, con: sists of a casing 50 closed atits open end by a curved cover plate 51. A plug 52 is provided in the casing50 to permit the introduction of a fluid medium into the internal space defined within the casing 50; cover plate 51 and a corrugated diaphragm disc 53 which divides the interior of the casing 50., This diaphragm disc 53'. is transparent and serves also due to its corrugated construction to permit expansion of the fluid 'conta-ined in the casing. Behind the. disc 53 in the casing 50 issmounted a lamp-socket54 and lamp 55. The lead; connections to the lamp are indicated-by the numeral56 and it will be. appreciated that these lead connections are. brought toany suitable source of electrical eniergy, as .foryexampl in the case ofan automobile, to the, battery.

l A ball screw 57 is threaded into/the casingSO and ser es with aissns y by i h. the v e it tevbe. mounted; To thisend', a clam'p'58'a'n'd pressure applying screw 59 areassociated with the ball portion of the screw 57 in a conventional manner and also are connected with a supporting bracket 60.

As before, the device is arranged with a compensator casing 61 in which is mounted a pair of compensator shafts 62, the axes of which are disposed transversely. Each compensator shaft 62 carries a pair of bar compensator magnets 63.

Mounted within: the space defined by the casing 50, cover. plate 5 1 and diaphragm disc 53 is a ball-like member structurally identical in all respects with the balllike member 23 of; the device shown in Figures 1 to 5 inclusive. Thus, the ball member 64 is composed of a lower casing element 70 housing a pair of bar magnets 71 in brackets 72 and a cover element 73. Also a weight 74, which may be of plastic material or of non-ferrous metal, is cemented in the bottom of casing element 70. The ball member 6 4is-mounted between a. pair of bearing cups 65 which in turn are maintained in their proper position by means; of tubular supports 66- welded, cemented, fused or otherwise joined. to the casing 50 and the bearing cups 65. In addition, a guide ring 67 is welded or. cemented to. the ball member 64 in a position, suchflhat. theguidei ring encircles in close proximity the upper bearing cup 65. Bymeans of this particular arrangement, the ball member 65 is capable of rotation only about a vertical axis which passes through the center of the bearing cups 65.

Theball member 64 is marked with the four points of the compass in a manner slightly different from that described with reference to, Figures 1 to 5 inclusive. In this particular instance, each point of the compass is shown atthree places on the ball member 64, once. at its equator, once above. the equator, and once below the equator. The cover plate 51, in place of being transparent, is instead arranged with three openings 68 corresponding in position to the three latitudes on the ball member 64 upon which the points of the compass are marked. The arrangement and correlation between the openings 68and thev markings of the points of the compass ls suchthat whenever a point of the compass shows through the opening 68 correspondingto the equator of the ball 'rnember 64, the same point of the compass will be displayed through the other two openings 68 in the cover 51 of the device. inasmuch as the cover plate 51 is curved it will be readily seen that a person sitting to the left of theiindi'cating; device, while. being unable to read with accuracy the. device through the central opening 68, wilhin effect, have a clear straight view of the upper opening 68 and hence will be able to accurately read the-device. Similarly, a person sitting to the right of the device, such as a co-pilot in an aircraft, will be able to read it through the lowermost opening 68. And, of course, a person sitting directly in front of the. device will readjit. through thecen'tral opening 68.

Referring nowto Figures 9 and 10, it will be noted that thearrangement shownfis. similar in many respects to the device illustrated in Figures- 6 to 8 inclusive with the exception that a flat cover plate is employed in place of the curved plate '51 and further, the guide ring 67 is absent so that the ball member 81 possesses universal movement. 'Al'so,'the ball" member 81 displays the four points of the compass solely about its equator. Inclination markings 83 are provided on the cover *plate 80- a'nd-also acceleration graduations 84 which are located vertically aligned with the lubb'erline 82 marked on plate; 80. It'will be apparent that upon accelerationof the device the Weight at the bottom of the ball will functionas-an. inertia-weight. This will have. theeifect of producing a rotation of the ball memberjBlabout a h iz ntal xis-Pa alle en hs pl n jo e co p t responsive toacceleration or deceleration forces. Thus, the markings at the equator of theball member 81 'will move vertically relative tograduations. 84 depending upon whether the deviceis being accelerated or decelerated.

The graduations 84 will, when suitably calibrated, provide a direct reading of the acceleration or deceleration that is at any moment taking place. All parts of the device shown and described with the exception of the magnets and possibly the ball screw and clamp can be made of a durable plastic or resinous material or other non-permeable material, such as non-ferrous metal.

Although the present invention has been shown and described with reference to particular embodiments, nevertheless various changes and modifications obvious to one skilled in the art are within the spirit, scope and contemplation of the present invention.

What is claimed is:

1. An instrument comprising a fluid-tight casing, a fluid contained in said casing, ball means located in said casing, magnet means contained in said ball means, said ball means and said magnet means together having a weight equivalent to the weight of an equal volume displacement of said fluid and having a center of gravity below the center of curvature of said ball means and a pair of bearing supports mounted within said casing on opposite sides of said ball means, each defining a ball-confining concavity the surface of which has a curvature complementary with the curvature of said ball means to confine said ball means between said bearing supports but leave said ball means free for rotation, said ball means being marked with indicia at three latitudes and said casing defining three openings corresponding in position to the three latitudes on said ball means.

2. An instrument comprising a fluid-tight casing, a fluid contained in said casing, ball means located in said casing, magnet means contained in said ball means, said ball means and said magnet means together having a weight equivalent to the weight of an equal volume displacement of said fluid and having a center of gravity below the center of curvature of said ball means and a pair of bearing supports mounted within said casing on opposite sides of said ball means, each defining a ball-confining concavity the surface of which has a curvature complementary with the curvature of said ball means to confine said ball means between said bearing supports but leave said ball means free for rotation, and means to restrain rotation of said ball means to one axis only.

3. An instrument comprising a fluid-tight casing, a fluid contained in said casing, ball means located in said casing, magnet means contained in said ball means, said ball means and said magnet means together having a weight equivalent to the weight of an equal volume displacement of said fluid and having a center of gravity below the center of curvature of said ball means, a pair of bearing supports mounted within said casing on opposite sides of said ball means, each defining a ball-confining concawty the surface of which has a curvature complementary with the curvature of said ball means to confine said ball means between said bearing supports but leave said ball means free for rotation, and a guide ring fixed to said ball means encircling one of said bearing supports to restrain rotation of said ball means to one axis only.

4. An instrument for a vehicle comprising a fluid-tight casing, a fluid contained in said casing, ball means located in said casing, magnet means contained in said ball means, said ball means and said magnet means together having a weight equivalent to the Weight of an equal volume displacement of said fluid and having a center of gravity below the center of curvature of said ball means, bearing support means within said casing to position said ball means but leave said ball means free for rotation, said ball means having compass points carried. on its equator, a transparent window in said casing to display said compass points in a position aligned with the direction of motion of said vehicle, a second set of compass points displaced from but parallel to said points on said equator of said ball means, a second transparent window over said second set of compass points, said second set of compass points and said second transparent window being offset from the direction of motion of said vehicle so that the true compass heading of said vehicle can be displayed at an angle to the direction of motion of said vehicle.

5. An instrument for a vehicle comprising a fluid-tight casing, a fluid contained in said casing, ball means located in said casing, magnet means contained in said ball means, said ball means and said magnet means together having a Weight equivalent to the weight of an equal volume displacement of said fluid and having a center of gravity below the center of curvature of said ball means, a pair of bearing supports mounted within said casing on opposite sides of said ball means, each defining a ball-confining concavity the surface of which has a curvature complementary with the curvature of said ball means to confine said ball means between said bearing supports but leave said ball means free for rotation, said ball means having compass points carried on its equator, a transparent window in said casing to display said compass points in a position aligned with the directionof motion of said vehicle, a second set of compass points displaced from but parallel to said points on said equator of said ball means, a second transparent window over said second set of compass points, said second set of cornpass points and said second transparent window being offset from the direction of motion of said vehicle so that the true compass heading of said vehicle can be displayed at an angle to the direction of motion of said vehicle.

References Cited in the file of this patent UNITED STATES PATENTS 1,397,490 Peradotto Nov. 15, 1921 1,589,039 Anschutz-Kaempfe June 15, 1926 1,968,556 Innis July 31, 1934 2,192,148 Otto Feb. 27, 1940 2,513,044 Page June 27, 1950 2,688,805 Annen Sept. 14, 1954 2,738,591 Spencer et al. Mar. 30, 1956 2,775,045 Kadlec Dec. 25, 1956 FOREIGN PATENTS 150.843 Great Britain Sept. 16, 1920 

